Association of pyrogenic exotoxin genes with pharyngitis and rheumatic fever/rheumatic heart disease among Indian isolates of Streptococcus pyogenes

Abstract

Aim: To monitor the presence of various pyrogenic exotoxin genes in strains of Streptococcus pyogenes isolated in India. Methods & Results: Isolates recovered from pharyngitis (52) and rheumatic fever (RF)/ rheumatic heart disease (RHD) (8) patients were analysed for the presence of toxin genes, speA, speB and speF, by PCR. The specificity of the products was confirmed by restriction enzyme digestion and Southern hybridization. Among the 60 isolates studied, the incidence of speA, speB and speF were 5(8.3%), 56(93.3%) and 53(88.3%), respectively. The expression of these genes was established in representative isolates by RT-PCR. Conclusions: Comparative analysis of frequency of the speA, speB and speF genes, among pharyngitis and RF/RHD associated isolates, showed higher incidence in RF/RHD (25%, 100%,100%) as compared to pharyngitis patients (5.8%, 92.3%, 86.5%), respectively. Significance of Study: The presence of the speA gene, which is usually associated with scarlet fever or toxic shock-like syndrome, within few Indian isolates may be indicative of new virulent strains circulating within the Indian community. High distribution of toxin genes among RF/RHD compared to pharyngitis isolates indicate their possible role in increased virulence.